A boat believed to be among the first in the world to use a hydrogen-powered internal combustion engine has undergone a sea trial.
The catamaran Cheetah set off from Ventnor earlier and took eight hours to circumnavigate the Isle of Wight.
Boatbuilder Cheetah Marine said it was the culmination of a three-year project to find "fuel for the future".
The firm said no greenhouse gases were emitted by the outboard engine, which produced only water vapour.
Lucy Strevens, of Cheetah Marine, said: "Previously craft have been powered by hydrogen fuel cells, but it doesn't appear there's been a boat running on internal combustion."
Hydrogen internal combustion engine
- Burns hydrogen to produce water as the only waste product
- Differs from hydrogen fuel cell systems which use an electro-chemical reaction to produce electricity
- Swiss inventor Francois Isaac de Rivaz is credited with creating a four-wheel prototype in 1807 using hydrogen contained in a balloon
- BMW and Ford are among manufacturers who have developed hydrogen internal combustion engine vehicles
- Hyundai and Toyota have introduced hydrogen vehicles to UK roads using fuel cell systems
- UK government pledged £7.5m in 2014 to prepare for the roll-out of hydrogen fuel cell vehicles
The 9.95m (32.6ft) catamaran was developed as part of the Isle of Wight's now-collapsed Ecoisland project which aimed to make the island energy self-sufficient by 2020.
Project partner ITM Power has built a marine refuelling station at Cheetah Marine's base in Ventnor, which produces hydrogen from mains water through electrolysis.
The station is part of a £4m government-funded project which has also led to the opening of a refuelling station near the M1 in Rotherham for hydrogen-powered vehicles.
The Ventnor firm said it had successfully tested a hydrogen-powered car which toured the island on 20 April.